1. Field of the Invention
This invention generally relates to a fascimile machine, and, in particular, to a facsimile machine having a page printing function.
2. Description of the Prior Art
A facsimile machine generally includes an image sensor for optically reading an original image to be transmitted, a recording unit for recording a received image on a recording medium and a communication unit for transmitting and receiving an image to and from another facsimile machine at a remote location. As the facsimile machine is being disseminated widely, there appears a growing demand for an even faster facsimile machine. In order to make a high-speed facsimile machine, it is necessary to provide not only a high-speed communication unit, but also a high-speed image sensor and recorder.
A vast majority of the facsimile machines currently in use employ a thermal printhead as a recording unit. Typically, the thermal printhead includes a plurality of heat-producing elements, such as electrical resistors, which are arranged in a spaced apart relationship at a predetermined pitch along a straight line extending in a direction transverse to the direction of advancement of a recording medium, which is normally a web of heat-sensitive paper stored in the form of a roll. In such a thermal printer type recording unit, the heat-sensitive paper in the form of a roll is unwound and transported in contact with the thermal printhead, to which an image signal to be recorded is supplied, and, thus, dark "burn" points are selectively formed on the heat-sensitive paper to form a printed image thereon.
In such a thermal printer type recording unit, the heat-sensitive paper is unrolled, an image is printed on the paper and the paper is cut to a desired size. The size is usually determined by the size of an original image received from a transmitter. In such a system, when a plurality of original documents different in size are received, there are produced cut sheets of printed paper different in size correspondingly. However, it is often desired that received images are all printed on the same size of cut sheets of paper even if the original documents have a variety of sizes. For this purpose, it has been proposed to provide a facsimile machine having a page printing function. The most typical example is a facsimile machine including a laser printer as its recording unit. In this case, a laser beam modulated by an image signal is deflected by a rotating polygon mirror and the deflected laser beam is scanned across a photosensitive member, thereby forming an electrostatic latent image thereon. Then, the latent image is developed by application of a developer and the thus developed image is then transferred to a transfer medium. In this case, since an electrophotographic process is used in printing a received image on a recording medium, image information is recorded ona page-by-page basis. In this respect, the laser printer falls onto the category of a page printer.
The page printer is fast in operation and allows to use plain paper as a recording medium, and, thus, the incorporation of a page printer into a facsimile machine as its recording unit presents an opportunity to provide a high-speed facsimile machine. Other than a laser printer, the page printer also includes an electrostatic printer which uses a multi-stylus head, to which an image signal is applied, for directly forming an electrostatic latent image on an imaging member, such as photosensitive or dielectric member. A further example of the page printer is a liquid crystal shutter printer which includes an array of liquid crystal shutters disposed between a light source and a photosensitive member, whereby the liquid crystal shutters are selectively operated in accordance with an image signal to form an electrostatic latent image on the photosensitive member.
A facsimile machine having a page printer is preferably provided with two or more cassettes for providing cut sheets of paper different in size. In such a facsimile machine, when an original image out of a predetermined size is received, it is recorded on two or more sheets of paper as divided. However, for example, when a facsimile machine receiving an original image having the A size width and a length beyond the predetermined size is provided with a pair of paper cassettes for B4 size and A4 size, the larger B4 size paper is first selected so as to minimize the number of recording cycles. In this case, however, if the last remaining portion of the original image is shorter in length than the A4 size, then the A4 size paper will be used to print this portion. This is inconvenient because the same original image is printed on two or more sheets of recording paper different in size, i.e., only the last sheet being different from the other sheets. In addition, if a facsimile machine is provided with a pair of cassettes containing B4 and A4 size cut sheets of recording paper, respectively, and a plurality of original images all in A5 size are being received, each of the A5 size original images is printed on a single cut sheet of B4 or A4 size paper, more than half of which is left unused.